NASA’s Carruthers Geocorona Observatory Begins Primary Science Mission - NASA Goddard

NASA’s Carruthers Geocorona Observatory began its 24-month primary science mission on March 1. The spacecraft, launched in September 2025, will focus its full efforts on studying Earth’s exosphere, the vast cloud of hydrogen that forms the outermost part of our atmosphere. 

Carruthers launched from NASA’s Kennedy Space Center on Sept. 24, 2025, and reached its target orbit around the Sun-Earth L1 Lagrange point on Jan. 8. From its vantage point at L1, about 1 million miles (1.5 million kilometers) from Earth toward the Sun, Carruthers has a constant view of Earth’s exosphere. Hydrogen atoms in the exosphere emit a bright ultraviolet glow, known as the geocorona, when they are illuminated by the Sun. Carruthers carries two ultraviolet imagers, one with a wide field of view and one with a narrow field, that together will capture images of the geocorona, revealing details that are otherwise invisible to the human eye.    

Over the next two years, Carruthers will watch how the exosphere expands and contracts as solar activity rises and falls, building the most complete record yet of the outermost layer of Earth’s atmosphere. These observations will reveal how Earth’s upper atmosphere responds to space weather, including solar storms and fast streams of solar wind, that affect satellites, communications, navigation signals, and other space-based systems. 

From a vantage point roughly one million miles closer to the Sun than Earth is, the Carruthers Geocorona Observatory will capture the most comprehensive views of the geocorona to date. The observations will reveal new insights into the structure of our atmosphere, how solar eruptions impact Earth, and how a planet’s surface water can escape to space, aiding the search for habitable planets elsewhere in the universe.
Credit: NASA’s Goddard Space Flight Center/Beth Anthony/Lacey Young

The exosphere is also where Earth slowly loses water to space. High-energy radiation can break apart water vapor into hydrogen and oxygen. The lighter hydrogen rises into the exosphere, and some atoms gain enough energy to escape Earth’s gravity forever. 

By studying this process at Earth and comparing it with atmospheric loss at Mars — a planet without a global magnetic field that lost its surface water over billions of years — scientists can better understand how planets lose or hold onto water over time. Because liquid water is essential for life, this research helps explain how long planets can remain habitable. 

The observatory is named for Dr. George R. Carruthers, whose ultraviolet instrument on Apollo 16 captured the first image of Earth’s geocorona from the Moon in 1972. Today’s mission continues that legacy by monitoring Earth’s outer atmosphere from deep space. 

The mission is led by Lara Waldrop of the University of Illinois Urbana-Champaign. The Space Sciences Laboratory at the University of California, Berkeley, leads mission implementation and payload development with Utah State University’s Space Dynamics Laboratory. The spacecraft was designed and built by BAE Systems. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the mission for the agency’s Heliophysics Division. 

Learn more about the Carruthers Geocorona Observatory at: 
https://science.nasa.gov/mission/carruthers-geocorona-observatory/ 

By Miles Hatfield 
NASA’s Goddard Space Flight Center, Greenbelt, Md.  

Source: NASA’s Carruthers Geocorona Observatory Begins Primary Science Mission  - NASA Science